Herein is disclosed a skimming and separation device for collecting material floating on the surface, that may be applied for collecting different kinds of pollutants, both solid and liquid, floating the water, but it is particularly devised and suited for collecting oil spilled on a water surface, including oil mixed with solid material.
In WO97/07292 and WO99/22078 various examples of prior art system are disclosed. Furthermore, U.S. Pat. Nos. 6,743,358, 7,807,059 and WO-2014/168577 disclose systems and devices related to the skimming and separation device to be disclosed in the present application.
These known systems and apparatuses comprise a collection vessel provided with a side wall comprising an upper wall part, a floater, which has some buoyancy. The floater is attached at its lower side to an essentially vertically arranged bellow allowing the floater to move from an upper position where no flow may enter the apparatus to a lower position forming a skimming weir allowing flow of water and debris to follow the contours of the floater and hit an open circular water compartment, the skimming compartment, with a water level that is determined by the speed of a propeller, the floating forces of the floater and the force gradients generated by differences in areas between the bellow floater.
In one known device disclosed in U.S. Pat. No. 6,743,358 the circular water compartment is at its upper end in open contact with atmospheric pressure and at its lower end delimited by a wall that holds the inlets of the collection vessels.
In WO-2014/168577 is disclosed a skimming and separation device provided with angulated nozzles, arranged to achieve a flow from the skimming compartment to the closed separating and collecting compartment. The angulated nozzles make the fluid including the pollutants to obtain a rotating motion within the separation and discharge compartment. The rotation of the fluid in the separation and discharge compartment makes a large horizontal area with a homogenous vertical speed. The discharge of fluid in the bottom of the separation compartment will generate a vertically oriented speed. This speed may be adjusted to be lower than the speed that the gravitational separation forces are generated to bring the pollutants towards the discharge area/compartment.
The separation compartment is delimited upward by a top wall with a discharge opening through which the oil and other pollutants may be expelled, by an equal exchange of water and/or pollutants entering into the separating and collecting compartment.
Water can be discharged or fed into the closed separating and collecting compartment through the collection vessel and through an opening in the bottom wall of the collection vessel, where a motor and propeller are arranged.
The collected debris is discharged from the collection compartment by reversing the propeller and feeding water into the separating and collection compartment. This leads to a backflow through the collecting vessels causing the skimming weir to be pressed against an overlying plate leading to a closure and pressure increase in the skimming and collecting compartment. This will further result in a pressure increase in the separating and collection compartment resulting in that collected oil in the collecting compartment will be pressurized and be expelled through the discharge opening into a suitable recipient.
The generated rotation of water and pollutants described in WO-2014/168577 is advantageous in many aspects. However, in some situations solid objects of various kinds are carried along by the oil and e.g. foam and may start clogging, this in turn may cause problems when being discharged from the separation and discharge compartment.
Furthermore, in some occasions the intermittent discharging phases often applied in the system of WO-2014/168577 may cause problems in transportation of pollutants from the separator to a suitable collecting tank. In addition, intermittent discharging phases are time consuming and may lower the overall capacity of the skimming and separation device.
It has further been shown that floating solid debris such as e.g. bottle caps, pieces of plastic, pieces of bark and wood, leaves or other plant debris that will not form a drop form takes considerably longer time to float upwards to the top of the separating unit for eventual discharge into a storage tank.
Thus, the object of the present invention is to achieve an improved skimming and separation device that eliminates, or at least mitigates, the above stated drawbacks. The improved device is less time-consuming to use, has a higher capacity, and has the capability of an improved handling of floating solid debris.